The ever growing number of bacterial strains and viral diseases which are resistant to antibiotics have made it necessary to introduce new kinds of drugs in order to treat humans and animals. Among the many present treatments and medicines, it has been known to use enzymes in monomeric form in order to provide therapeutic effects in patients afflicted with various diseases. Enzymes are catalytically active proteins which perform almost all major life processes in organisms. Thus, many enzymes, either individually or in certain combinations, have been isolated for their physiocochemical, physiological, or biological effects.
Among the various enzymes for which certain therapeutic effects have been documented are lysozyme and ribonuclease. Lysozyme has been known since 1922, the year when it was discovered by Fleming. Only after 1950, however, were the enzymatic functions of lysozyme revealed. Since this time, the compound has been a subject of intense physiocochemical, physiologic and clinical research, but the extent of this compound's biological significance has still yet to be determined. Thus far, lysozyme has been observed to have various therapeutic properties, such as antiviral, antibacterial, anti-inflammatory and antihistaminic properties. The antibacterial effect appears to be based on the hydrolysis of the beta-1-4-glycoside bond between N-acetylomuraminic acid and N-acetyloglucosamine, both contained in the bacterial wall.
The presence of lysozyme in phagocytotic cells is also well documented. Research in this area has shown that the intracellular lysozyme contained in lysozymes is responsible for digesting the phagocytized bacteria. In humans, lysozyme has been observed to stimulate phagocytosis at a physiological concentration of 10-400 mg/ml.
Other properties of lysozyme have also been documented. For instance, it appears that lysozyme reduces body temperature during the infection process, where temperature is a response to endogenic pyrogens liberated by toxins. It also appears that lysozyme participates in immunological processes by stimulating the synthesis of gamma globulins, opsonins, and other antibodies. Still further, it has been suggested that lysozyme has a strong anti-inflammatory effect. Despite these known beneficial properties of lysozyme, despite numerous research projects and the production of pharmaceutical preparations based on lysozyme, the use of this enzyme for therapeutical purposes has been vastly limited.
Another group of enzymes which have been studied for their various biological effects are the ribonucleases. These are a group of enzymes commonly found in many animal and plant organisms as well as in bacterial cells. The study of their properties and research into methods of isolation was initiated in 1955 by Schmidt and McDonald. Among the findings based on this enzyme, it was found that in cancerous tissues the activity of ribonucleases was considerable reduced. For example, it was discovered that leukemogenic viruses drastically diminished the activity of acid ribonuclease in mice. Also, in mice with viral leukemia, a considerable decrease in acid ribonuclease activity was found in mitochondria and microsome fractions obtained from the spleen tissue of those animals.
The studies cited above suggest that the decrease in activity of ribonuclease is somehow closely connected with the infections caused by the virus. It has thus been suggested that the ribonuclease enzymes may possess some antiviral activity. Again, however, at present, there have been no known reports on the preparation of compounds employing this enzyme as an antiviral agent.
One of the main reasons why such potentially beneficial enzymes have not as yet been widely used for their therapeutic effects is the observed cytotoxic effect of the monomeric forms of these and other enzymes. In tests with cultured fibroblasts, there has been an observed cytotoxic effect from both the lysozyme and ribonuclease monomers at even very small quantities. Clearly, the potential beneficial effects from these and other enzymes could be achieved if an effective way of controlling these cytotoxic effects could be developed. What is desired, therefore, is to develop compositions based on lysozyme, ribonuclease, or other similar enzymes, which can effectively be used to treat viral or bacterial disease or other harmful conditions without the cytotoxic effects normally observed when the enzymes are used in the monomeric form.